1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer and the like.
2. Related Background Art
In some cases, the desired number of imaged sheets (single or plural) outputted from an image forming apparatus for forming an image on sheets supplied one by one are bundled together to form a booklet. In many cases, a surface sheet (cover) including a front sheet portion, a rear sheet portion and a back sheet portion is integrally attached to the booklet.
The surface sheet for the booklet is generally formed by the image forming apparatus. In this case, after the number of imaged sheets for constituting the booklet are outputted, the surface sheet is formed. In the formation of the surface sheet for the booklet, although a size of a sheet used as the surface sheet must be selected, in this case, it is required that a size of the back sheet portion (corresponding to a thickness of the booklet) is determined. The size of the back sheet portion can be determined by (thickness of sheet) x (the number of sheets for constituting the booklet). However, in an image forming apparatus in which plural color toner images are transferred onto the sheet in a superimposed fashion, thicknesses of the transferred toner images on the sheet must be taken in consideration.
In the conventional image forming apparatuses, when the surface sheet is formed, generally, data including the thickness of the sheet and the number of sheets constituting the booklet has been inputted to a calculation portion by an operator himself to determine the size of the back surface portion of the surface sheet. However, in such a case where the operator manually inputs the data, if the operator erroneously inputs the data, the correct size cannot be calculated in the calculation portion. As a result, an unwanted surface sheet is outputted from the image forming apparatus, thereby consuming the sheet uselessly.